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Math.Round Method (Double)

Rounds a double-precision floating-point value to the nearest integer.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

public static double Round (
	double a
)
public static double Round (
	double a
)
public static function Round (
	a : double
) : double
Not applicable.

Parameters

a

A double-precision floating-point number to be rounded.

Return Value

The integer nearest a. If the fractional component of a is halfway between two integers, one of which is even and the other odd, then the even number is returned.

The behavior of this method follows IEEE Standard 754, section 4. This kind of rounding is sometimes called rounding to nearest, or banker's rounding. It

minimizes rounding errors that result from consistently rounding a midpoint value in a single direction.

To control the type of rounding used by the Round method, call the Math.Round(Double,MidpointRounding) overload.

The following example demonstrates rounding to nearest integer value.

Math.Round(4.4); //Returns 4.0.
Math.Round(4.5); //Returns 4.0.
Math.Round(4.6); //Returns 5.0.

System.Math.Round(4.4); //Returns 4.0.
System.Math.Round(4.5); //Returns 4.0.
System.Math.Round(4.6); //Returns 5.0.

System.Math.Round(4.4) //Returns 4.0.
System.Math.Round(4.5) //Returns 4.0.
System.Math.Round(4.6) //Returns 5.0.

The following code sample uses Round to assist in the computation of the inner angles of a given trapezoid.

/// <summary>
/// The following class represents simple functionallity of the Trapezoid
/// </summary>
class MathTrapezoidSample
{
    private double m_longBase;
    private double m_shortBase;
    private double m_leftLeg;
    private double m_rightLeg;

    public MathTrapezoidSample(double longbase, double shortbase, double leftLeg, double rightLeg)
    {
        m_longBase = Math.Abs(longbase);
        m_shortBase = Math.Abs(shortbase);
        m_leftLeg = Math.Abs(leftLeg);
        m_rightLeg = Math.Abs(rightLeg);
    }

    private double GetRightSmallBase()
    {
        return (Math.Pow(m_rightLeg,2.0) - Math.Pow(m_leftLeg,2.0) + Math.Pow(m_longBase,2.0) + Math.Pow(m_shortBase,2.0) - 2* m_shortBase * m_longBase)/ (2*(m_longBase - m_shortBase));
    }

    public double GetHeight()
    {
        double x = GetRightSmallBase();
        return Math.Sqrt(Math.Pow(m_rightLeg,2.0) - Math.Pow(x,2.0));
    }

    public double GetSquare()
    {
        return GetHeight() * m_longBase / 2.0;
    }

    public double GetLeftBaseRadianAngle()
    {
        double sinX = GetHeight()/m_leftLeg;
        return Math.Round(Math.Asin(sinX),2);
    }

    public double GetRightBaseRadianAngle()
    {
        double x = GetRightSmallBase();
        double cosX = (Math.Pow(m_rightLeg,2.0) + Math.Pow(x,2.0) - Math.Pow(GetHeight(),2.0))/(2*x*m_rightLeg);
        return Math.Round(Math.Acos(cosX),2);
    }

    public double GetLeftBaseDegreeAngle()
    {
        double x = GetLeftBaseRadianAngle() * 180/ Math.PI;
        return Math.Round(x,2);
    }

    public double GetRightBaseDegreeAngle()
    {
        double x = GetRightBaseRadianAngle() * 180/ Math.PI;
        return Math.Round(x,2);
    }

    static void Main(string[] args)
    {
        MathTrapezoidSample trpz = new MathTrapezoidSample(20.0, 10.0, 8.0, 6.0);
        Console.WriteLine("The trpezoid's bases are 20.0 and 10.0, the trapezoid's legs are 8.0 and 6.0");
        double h = trpz.GetHeight();
        Console.WriteLine("Trapezoid height is: " + h.ToString());
        double dxR = trpz.GetLeftBaseRadianAngle();
        Console.WriteLine("Trapezoid left base angle is: " + dxR.ToString() + " Radians");
        double dyR = trpz.GetRightBaseRadianAngle();
        Console.WriteLine("Trapezoid right base angle is: " + dyR.ToString() + " Radians");
        double dxD = trpz.GetLeftBaseDegreeAngle();
        Console.WriteLine("Trapezoid left base angle is: " + dxD.ToString() + " Degrees");
        double dyD = trpz.GetRightBaseDegreeAngle();
        Console.WriteLine("Trapezoid left base angle is: " + dyD.ToString() + " Degrees");
    }
}

/// <summary>
/// The following class represents simple functionallity of the Trapezoid
/// </summary>
class MathTrapezoidSample
{
    private double mLongBase;
    private double mShortBase;
    private double mLeftLeg;
    private double mRightLeg;
    public MathTrapezoidSample(double longBase, double shortBase, 
        double leftLeg, double rightLeg)
    {
        mLongBase = System.Math.Abs(longBase);
        mShortBase = System.Math.Abs(shortBase);
        mLeftLeg = System.Math.Abs(leftLeg);
        mRightLeg = System.Math.Abs(rightLeg);
    } //MathTrapezoidSample

    private double GetRightSmallBase()
    {
        return (System.Math.Pow(mRightLeg, 2.0) 
            - System.Math.Pow(mLeftLeg, 2.0) 
            + System.Math.Pow(mLongBase, 2.0) 
            + System.Math.Pow(mShortBase, 2.0) 
            - 2 * mShortBase * mLongBase) / (2 * (mLongBase - mShortBase));
    } //GetRightSmallBase

    public double GetHeight()
    {
        double x = GetRightSmallBase();
        return System.Math.Sqrt(System.Math.Pow(mRightLeg, 2.0) 
            - System.Math.Pow(x, 2.0));
    } //GetHeight

    public double GetSquare()
    {
        return GetHeight() * mLongBase / 2.0;
    } //GetSquare

    public double GetLeftBaseRadianAngle()
    {
        double sinX = GetHeight() / mLeftLeg;
        return System.Math.Round(System.Math.Asin(sinX), 2);
    } //GetLeftBaseRadianAngle

    public double GetRightBaseRadianAngle()
    {
        double x = GetRightSmallBase();
        double cosX = (System.Math.Pow(mRightLeg, 2.0) 
               + System.Math.Pow(x, 2.0) 
               - System.Math.Pow(GetHeight(), 2.0)) / (2 * x * mRightLeg);
        return System.Math.Round(System.Math.Acos(cosX), 2);
    } //GetRightBaseRadianAngle

    public double GetLeftBaseDegreeAngle()
    {
        double x = GetLeftBaseRadianAngle() * 180 / System.Math.PI;
        return System.Math.Round(x, 2);
    } //GetLeftBaseDegreeAngle

    public double GetRightBaseDegreeAngle()
    {
        double x = GetRightBaseRadianAngle() * 180 / System.Math.PI;
        return System.Math.Round(x, 2);
    } //GetRightBaseDegreeAngle

    public static void main(String[] args)
    {
        MathTrapezoidSample trpz = 
            new MathTrapezoidSample(20.0, 10.0, 8.0, 6.0);
        Console.WriteLine("The trpezoid's bases are 20.0 and 10.0,"
            + " the trapezoid's legs are 8.0 and 6.0");
        double h = trpz.GetHeight();
        Console.WriteLine("Trapezoid height is: " 
            + System.Convert.ToString(h));
        double dxR = trpz.GetLeftBaseRadianAngle();
        Console.WriteLine("Trapezoid left base angle is: " 
            + System.Convert.ToString(dxR) + " Radians");
        double dyR = trpz.GetRightBaseRadianAngle();
        Console.WriteLine("Trapezoid right base angle is: " 
            + System.Convert.ToString(dyR) + " Radians");
        double dxD = trpz.GetLeftBaseDegreeAngle();
        Console.WriteLine("Trapezoid left base angle is: " 
            + System.Convert.ToString(dxD) + " Degrees");
        double dyD = trpz.GetRightBaseDegreeAngle();
        Console.WriteLine("Trapezoid left base angle is: " 
            + System.Convert.ToString(dyD) + " Degrees");
    } //main
} //MathTrapezoidSample

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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